We report a clinical case of a rare variant of pemphigus - pemphigus herpetiformis - which combines the clinical features of dermatitis herpetiformis with the immunological findings of pemphigus. Due to its atypical presentation, it is frequently misdiagnosed as dermatitis herpetiformis. It is basically characterized by the herpetiform pattern of skin lesions, severe pruritus and by the presence of eosinophilic spongiosis confirmed on histopathology. We call attention to the excellent response to dapsone.

A 63-year-old Caucasian man presented with a two-month history of an intensely pruritic, symmetric and polymorphous skin eruption. His past medical history was unremarkable.

On examination, we observed multiple papules, vesicles, pustules and crusted excoriations on an erythematous base, especially over the buttocks, legs and arms (Figure 1). The oral and genital mucosas were spared. Nikolsky's sign was negative.

The patient was treated with 100 mg/day dapsone and showed an excellent response. After a year, he was free of the disease on a maintenance dose of 50 mg dapsone daily.

DISCUSSION

Pemphigus herpetiformis (PH) was diagnosed based on clinical, histopathological and immunological findings.

PH was first introduced by Jablonska et al. in 1975. 1 It is considered a rare variant of pemphigus which combines the clinical features of dermatitis herpetiformis with the immunological findings of pemphigus. Due to its rarity and atypical presentation, PH is frequently misdiagnosed as dermatitis herpetiformis, pemphigus foliaceus, bullous pemphigoid and several other autoimmune bullous conditions.

Clinically, patients present with severe intractable pruritus with cutaneous lesions arranged in a herpetiform pattern, resembling the clinical picture of dermatitis herpetiformis. Histological findings vary according to the evolution of skin lesions, and typical findings of pemphigus emerge only later in the disease process. 2 Therefore, several biopsies may be needed to establish a correct diagnosis. In the early stages, biopsy specimens show eosinophilic spongiosis with or without acantholytic cells and intraepidermal vesicles and bullae filled with neutrophils and eosinophils. This is an important but non-diagnostic histological reaction and it may be the initial pattern of a pre-acantholytic inflammatory stage. The finding of eosinophilic spongiosis should prompt a recommendation for other diagnostic studies. Because the clinical presentation of the disease and the histological findings are often atypical, the most consistent test for diagnosis of PH is immunofluorescence. 3 Direct immunofluorescence (DIF) performed on perilesional skin revealed intraepithelial intercellular IgG deposits, which is the typical finding. 3 Most PH autoantibodies target desmoglein (Dsg) 1, with exceptional cases manifesting autoantibodies against Dsg 3, implicating the predominant autoimmunity similar to pemphigus foliaceus rather than pemphigus vulgaris. 4 Several cases of PH without anti-Dsg 1-3 autoantibodies were reported. 4 More recently, it has been found that many patients with PH also show autoantibodies against desmocollin. 5

Several papers have reported clinical cases of HP associated with some neoplasms, HIV infection and medication. 6,7,8 Diagnostic investigations in our patient showed no evidence of associated systemic disease, and he was not taking any drugs.

In general, the disease shows a benign course, with a good response to treatment. Our patient had been initially treated with prednisolone without any benefit. Therefore, he was started on dapsone with total response. Dapsone is considered the best drug for the treatment of PH with doses ranging from 100 to 300 mg daily. 2 It may be given as monotherapy or in association with corticosteroids and immunosuppressant drugs. It is known that superficial forms of pemphigus, those with low or negative antibody titers and histological features of eosinophilic spongiosis, respond well to dapsone. 9 However, some cases of PF and PV in patients with PH have been reported. 2,9 In these cases, systemic corticosteroids in combination with immunosuppressants may be required.